Apparatus for solvent removal

ABSTRACT

An apparatus wherein a superheated vapor and/or gas is employed as the sole source of heat to volatilize a volatilizable liquid from a base material without subjecting the material to stresses normally attendant with drying and movement of materials through drying zones. The apparatus, a chamber closed to the ambient atmosphere except for an opening for ingress and egress of the material into the interior of the chamber, contains a material moving means to carry the material through several traverses of the chamber without subjecting the material to stress during the traverse. The sole source of heat to volatilize the liquid on the material is superheated vapors and/or gases circulated into and out of the chamber and through the material. The interior of the chamber is provided with a plurality of moving belts which are staggered one below the other to receive the incoming material and move it transversely across the chamber several times. The uppermost belt moves the material from the entrance to the chamber across the chamber and deposits it onto the next lower belt moving in the opposite direction. Several of such belts may be employed. A final belt in the lower interior of the chamber moves the material across the interior to the exit side of the interior where the material is removed from the exit. The apparatus also includes a means to remove the vapors in excess of those necessary to fill the chamber and the recirculating superheat means and to move the vapors from the interior of the chamber through the wet material and into the superheating means. To accomplish the latter effectively and efficiently, a vapor or gas collecting plenum is provided beneath each belt to withdraw the vapor and/or gases from the interior of the chamber and deliver these gases to the superheating means. The vapors and/or gases which are withdrawn are superheated above their boiling point and the boiling point of the liquid to be removed from the material and returned to the chamber as the essential source of heat to effect the evaporation of the volatilizable liquid which entered the chamber on the material. The apparatus of the present invention provides in addition to a means for removing the volatilizable liquid from the textile material or particulate material a means for accomplishing the removal without subjecting the textile material to any stresses such as stretching or the particulate material to any stresses such as normally result from the grinding and attrition of materials moving through the conventional particulate drying processes.

United States Patent 1191 Ryan et al.

1451 Sept. 30, 1975 1 APPARATUS FOR SOLVENT REMOVAL [75] Inventors: Richard A. Ryan, Eddington;

Vincent A. Galeone, Warrington. both of Pa.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

221 Filed: Dec. 19, 1973 21 Appl. No.: 426,149

Primary E.\uminerCarroll B. Dority, Jr. Assistant E.\'an1inerLarry l. Schwartz Attorney. Agenl. or FirmGlwynn R. Baker [57] ABSTRACT An apparatus wherein a superheated vapor and/or gas is employed as the sole source of heat to volatilize a volatilizable liquid from a base material without subjecting the material to stresses normally attendant with drying and movement of materials through drying zones. The apparatus, a chamber closed to the ambient atmosphere except for an opening for ingress and egress of the material into the interior of the chamber. contains a material moving means to carry the material through several traverses of the chamber without subjecting the material to stress during the traverse. The sole source of heat to volatilize the liquid on the material is superheated vapors and/or gases circulated into and out of the chamber and through the material. The interior of the chamber is provided with a plurality of moving belts which are staggered one below the other to receive the incoming material and move it transversely across the chamber several times. The uppermost belt moves the material from the entrance to the chamber across the chamber and deposits it onto the next lower belt moving in the opposite direction. Several of such belts may be employed. A final belt in the lower interior of the chamber moves the material across the interior to the exit side of the interior where the material is removed from the exit. The apparatus also includes a means to remove the vapors in excess of those necessary to fill the chamber and the recirculating superheat means and to move the vapors from the interior of the chamber through the wet material and into the superheating means. To accomplish the latter effectively and efficiently, a vapor or gas collecting plenum is provided beneath each belt to withdraw the vapor and/or gases from the interior of the chamber and deliver these gases to the superheating means. The vapors and/or gases which are withdrawn are superheated above their boiling point and the boiling point of the liquid to be removed from the material and returned to the chamber as the essential source of heat to effect the evaporation of the volatilizable liquid which entered the chamber on the material.

The apparatus of the present invention provides in addition to a means for removing the volatilizable liquid from the textile material or particulate material a means for accomplishing the removal without subjecting the textile material to any stresses such as stretching or the particulate material to any stresses such as normally result from the grinding and attrition of materials moving through the conventional particulate drying processes.

1 Claim, 2 Drawing Figures US. Patent Sep.t.30,1975 sheetlofz 3,908,285

US. Patent Sept. 30,1975 Sheet 2 of 2 3,908,285

SUPER HEATER APPARATUS FOR SOLVENT REMOVAL The apparatus of the present invention provides in addition to a means for removing the volatilizable liqaid from the textile material or particulate material a means for accomplishing the removal without subjecting the textile material to any stresses such as stretching or the particulate material to any stresses such as normally result from the grinding and attrition of materials moving through the conventional particulate drying processes.

BRIEF DESCRIPTION OF INVENTION In general, the apparatus of the present invention comprises a basically rectangular chamber provided with a series of belts or screens which rotate about pairs of support cylinders at least one of which cylinders of each belt is driven, preferably by exterior means. The chamber has an opening, preferably on opposite sides to provide a means of ingress and egress of the material into the interior of the chamber. Positioned below each belt or screen material carrying-surface is a plenum associated with a means to withdraw through the plenum gases or vapors which fill the interior of the chamber and superheat the vapors for return to the chamber. Associated with the ingress and egress to the interior of the chamber are a series of gas confining means, conveniently condensing coils, surrounding the upper peripheral limit of the vapor zone which is normally just below the opening of the ingress and egress.

The belts or screens which are located within the chamber are staggered one below the other. By this configuration, material is moved transversely across the apparatus on the uppermost belt and will fall onto a belt moving in the opposite direction, thus carrying the material back across the interior where it is dropped to a third belt which is moving in the same direction as the first belt. The third belt carries the material transversely across the chamber to a point where it is picked up and removed to the egress slot in the apparatus walls. More than three belts may be employed if a high volume of material is processed or a longer or slower drying period is desired.

One embodiment of the present invention, i.e., an apparatus for processing fabric, web or like ,materials, that is, textile materials, to remove a liquid which has been applied in a previous step, provides a means for recovering the liquid in the form ofa vapor, and for the movement of the fabric through the apparatus without subjecting the web or like material to stresses, such as stretching, contact with heated rolls, etc. The apparatus of this embodiment comprises a basically rectangular chamber provided with a series of belts or screens which rotate about pairs of support cylinders at least one of which is driven, preferably by exterior means. A plurality of belts are arranged within the enclosure in a staggered manner to provide for the transfer of the fabric, web or like material from an upper belt to a iowcr belt which is being driven in the opposite direction to the upper belt, thus transferring the material transversely across the interior several times. Each belt or screen is porous and provided with a plenum below the belt conveying surfaces into which the gaseous heat-transfer medium can be drawn after direct contact with the fabric web or like material moving with the belt. Means are provided for removing the gases or vapors withdrawn from the chamber into the plenum, reheating and recirculating the vapors to the chamber at a temperature to facilitate the removal of the liquid, e.g., solvent, on the fabric or web. Means are also provided for confining the gas or vapor within the enclosure below the entrance and exit, taking advantage of the physical characteristics of the vapor or gases being more dense than the ambient air. The means for maintaining the vapor level are conveniently condensing coils surrounding the upper peripheral limit of the vapor zone. These means, when associated with a condensate collecting trough, also provide for removal of vapors in excess of those necessary to fill the chamber or enclosure and the vapor recycling system.

Thus, the apparatus of the present invention comprises an enlosure having an opening for inlet of a fabric, web or like material and outlet therefrom. The interior of the chamber is provided with a series of condensing coils through which a cooling fluid will pass and a collecting trough below the condensing coils. The coils and trough either substantially surround the entire inner peripheral area of the enclosure near the inlet and outlet or are arranged below each of the inlet and outlet. Below these collecting troughs, there is provided a series of, for example, three belts at three different levels within the enclosure, each belt being staggered from the one above in a manner such that any fabric or web or like material being carried along the upper belts surface will drop over the end of the belt in the direction of movement and onto the belt below which is moving in the opposite direction. Associated with each belt system is a plenum through which a gas or vapor can be withdrawn from the interior. This withdrawal is through the web and belt. In addition, there is provided a means for directing the vapors and/or gases to a heating means after which they are returned to the interior as the essential solvent removal medium.

The present invention provides an apparatus for removing liquids which are vaporizable, from a fabric, web or like material in a manner such that the fabric, web or like material is not subjected to any tensions until the solvent or liquid has been removed. Such a configuration enables the removal of solvent from woven and nonwoven, knitted and like fabrics and webs which it is desired to maintain in a tensionless condition during the solvent removal,

The present invention is an improved method for removing liquids which are vaporizable from fabric, web and the like which eliminates the contact of fabrics with cans or rollers, which cans or rollers may be at temperatures above the fabric distortion or damage point in order to effectively and efficiently remove the solvent or liquid. An additional advantage of the present invention is that one does not depend upon the tension in the fabric, web or like material to maintain integral surface contact necessary for efficient heat transfer. Additionally, the present invention permits the removal of solvent or liquid from a nonwoven type material. It is a further advantage of the present invention that sophisticated baffling is not required to obtain efficient transfer of heat to the webbed fabric. Finally, the present invention eliminates the tensions normally associated with movement of textile materials through a heating zone.

Another embodiment of the present invention permits the removal of liquids from particulate matter without any substantial attrition of the material during passage through the chamber. In this embodiment of the apparatus of the present invention, a particulate material can be dried with a gas and/or vapor effieiently and economically because during the move ment of the material through the apparatus, the material is subjected to overturning, exposing different particles to the drying gases at the surface without the usual attrition resulting from the grinding effect of screw conveyers or constant rolling contact such as found in a kiln or the like. In this embodiment, it may be advantageous to convey the particulate matter from the lowest conveyer to an exit established near the level of the lowest conveyer. However, if a chlorinated solvent is to be employed as the vaporous drying medium, then it is preferable to convey the material to a point above the vapor zone and out an exit above the vapor zone as described in the foregoing description.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a side view of the preferred embodiment of the present invention.

FIG. 2 is a cross sectional view along line 22 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION The following description of the apparatus of the present invention has particular reference to the drawings.

One embodiment of the present invention, as illustrated in FIG. 1, is a generally rectangular box-like enclosure having an inlet 11 and an outlet 12 in the upper reaches of the sides 13 and 14, respectively. Located below the inlet 11 and outlet 12 are a series of coils l5 and a trough 15a extending around the inner periphery of the enclosure 10. The remainder of the interior of enclosure 10 is provided with rotating endless belts 16, 17 and 18, staggered one below the other to provide a surface upon which a fabric, web or like material moving to the end of one belt can be dropped onto the next lower belt. Located beneath the upper surface, the material carrying surface, of each endless belt are vapor withdrawal ducts 19, 20 and 21, respectively. This ducting is connected to an exhaust blower, and superheater (not shown), and the gas or vapors are removed from the enclosure 10 through the ducting, The gas or vapor is returned to the enclosure through the ducting 22 into the enclosure below the inlet 11 and outlet 12 and preferably below the trough 15a.

Located within enclosure 10 are guide roll 23 for directing the fabric onto the conveyer belt 16 and pickup rolls 24 and 25 for withdrawing the fabric from belt 18.

In operation of the apparatus above described, a chlorinated solvent, for example, is vaporized into the interior of the chamber and the superheating means is operated to create within the chamber a zone of superheated vapors sufficient to fill the entire chamber up to the condensing coils. The condensing coils, of course, have previously been connected to a source of cool or cold water and establish an upper limit of the zone of superheated vapors. Any space above the superheated vapor line, that is the space substantially vapor free above the cooling coils, is substantially quiescent and the movement of material into the interior of the chamher and out of the interior of the chamber therefore does not remove any substantial amount of solvent vapors from the apparatus. Once the vapor zone has been established within the interior of the chamber, the belts and conveyers are started and the material to be dried is introduced at a rate such that when the materialhas reached the lower belt near its end, it is substantially dry and has achieved approximately the temperature of the vapor in the zone. Thus, as the material is withdrawn through the vapor zone to the point of egress, there is no further condensation of any vapors upon the material, be it the fabric or be it the particulate matter and thus the particulate matter or textile is removed from the apparatus free from solvent. The operation of the particular configuration described above can be used to dry knit fabrics or particulate matter in which latter case no grinding action or attrition due to fines is observed as the particles are moved through the zone of drying.

We claim:

1. An apparatus for removing solvent from a material and recovering the solvent so removed, which comprises:

a. an enclosure having a means of ingress and egress to its interior, a series of condensing coils about the inner periphery below the ingress and egress and a trough below said coils for collecting condensate;

b. a series of endless horizontal belts forming belt loops, one below the other, positioned below the said trough, to receive the material from the ingress means, move it transversely across the enclosure and drop it onto the next lower belt, the lowest belt extending beyond the other belts and having a direction of travel towards the egress and associated with pick-up means for the material for movement to the egress;

c. a means for introducing a vapor into the enclosure below the condensing troughs;

. a means for withdrawing vapor from the enclosure,

said means being positioned within the belt loops to cause vapors to be withdrawn through the material on the belt and the belt;

e. a means for heating the withdrawn vapors and means to return said so-heated vapors to said vapor introducing means;

f. means associated with said belts for moving said belts; and

g. means for delivering material from said ingress to said belts and means for removing said material from said belts to said egress. 

1. An apparatus for removing solvent from a material and recovering the solvent so removed, which comprises: a. an enclosure having a means of ingress and egress to its interior, a series of condensing coils about the inner periphery below the ingress and egress and a trough below said coils for collecting condensate; b. a series of endless horizontal belts forming belt loops, one below the other, positioned below the said trough, to receive the material from the ingress means, move it transversely across the enclosure and drop it onto the next lower belt, the lowest belt extending beyond the other belts and having a direction of travel towards the egress and associated with pick-up means for the material for movement to the egress; c. a means for introducing a vapor into the enclosure below the condensing troughs; d. a means for withdrawing vapor from the enclosure, said means being positioned within the belt loops to cause vapors to be withdrawn through the material on the belt and the belt; e. a means for heating the withdrawn vapors and means to return said so-heated vapors to said vapor introducing means; f. means associated with said belts for moving said belts; and g. means for delivering material from said ingress to said belts and means for removing said material from said belts to said egress. 